Is Mechila through email or instant message considered a complete mechila?
There is a certain debate among authorities concerning whether mechilah requires an expression of forgiveness, or whether forgiveness of the heart is sufficient. Some point out the words of Rabbeinu Bachya (Bereishis 50:17) concerning Yosef’s brothers, who seems to imply that a statement of forgiveness is required. However, the generally accepted opinion is that mechilah depends first and foremost on the heart (see, at length, Chayim Beyad no. 57). Even if a person states that he forgives another, his forgiveness is only valid if he really means it (see She’arim Hametzuyanim Behalachah 131:8). In the case of email of messaging, the statement of mechilah is no worse than any other expression of mechilah, and the mechilah can certainly be complete. However, because of the ease with which such messages are written, one should ensure that the person granting mechilah really means it. It all depends on the heart.